diff --git a/functions/what_is_my_ip/.envrc b/functions/what_is_my_ip/.envrc
new file mode 100644
index 0000000..3550a30
--- /dev/null
+++ b/functions/what_is_my_ip/.envrc
@@ -0,0 +1 @@
+use flake
diff --git a/functions/what_is_my_ip/Dockerfile b/functions/what_is_my_ip/Dockerfile
new file mode 100644
index 0000000..d4f1541
--- /dev/null
+++ b/functions/what_is_my_ip/Dockerfile
@@ -0,0 +1,32 @@
+
+# syntax = docker/dockerfile:1.4
+FROM nixos/nix:2.21.1@sha256:3f6c77ee4d2c82e472e64e6cd7087241dc391421a0b42c22e6849c586d5398d9 AS builder
+
+WORKDIR /tmp/build
+RUN mkdir /tmp/nix-store-closure
+
+# ignore SC2046 because the output of nix-store -qR will never have spaces - this is safe here
+# hadolint ignore=SC2046
+RUN --mount=type=cache,target=/nix,from=nixos/nix:2.21.1,source=/nix \
+    --mount=type=cache,target=/root/.cache \
+    --mount=type=bind,target=/tmp/build \
+    <<EOF
+  nix \
+    --extra-experimental-features "nix-command flakes" \
+    --option filter-syscalls false \
+    --extra-trusted-substituters "https://cache.iog.io" \
+    --extra-trusted-public-keys "hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=" \
+    --show-trace \
+    --log-format raw \
+    build . --out-link /tmp/output/result
+  cp -R $(nix-store -qR /tmp/output/result) /tmp/nix-store-closure
+EOF
+
+FROM scratch
+
+WORKDIR /app
+
+COPY --from=builder /tmp/nix-store-closure /nix/store
+COPY --from=builder /tmp/output/ /app/
+
+ENTRYPOINT ["/app/result/bin/entrypoint"]
diff --git a/functions/what_is_my_ip/flake.lock b/functions/what_is_my_ip/flake.lock
new file mode 100644
index 0000000..b6922f6
--- /dev/null
+++ b/functions/what_is_my_ip/flake.lock
@@ -0,0 +1,61 @@
+{
+  "nodes": {
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1710146030,
+        "narHash": "sha256-SZ5L6eA7HJ/nmkzGG7/ISclqe6oZdOZTNoesiInkXPQ=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "b1d9ab70662946ef0850d488da1c9019f3a9752a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1718447546,
+        "narHash": "sha256-JHuXsrC9pr4kA4n7LuuPfWFJUVlDBVJ1TXDVpHEuUgM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "842253bf992c3a7157b67600c2857193f126563a",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-23.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-utils": "flake-utils",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/functions/what_is_my_ip/flake.nix b/functions/what_is_my_ip/flake.nix
new file mode 100644
index 0000000..83e62ef
--- /dev/null
+++ b/functions/what_is_my_ip/flake.nix
@@ -0,0 +1,28 @@
+{
+  description = "what is my ip";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils, ...}@inputs:
+
+    flake-utils.lib.eachDefaultSystem
+      (system:
+        let
+          pkgs = import nixpkgs {
+            inherit system;
+          };
+
+        in rec
+        {
+          packages = rec {
+
+            default = pkgs.writeShellScriptBin "entrypoint" ''
+              ${pkgs.curl}/bin/curl -s http://httpbin.org/get | \
+                  ${pkgs.jq}/bin/jq --raw-output .origin
+            '';
+          };
+        });
+}
diff --git a/functions/what_is_my_ip/runbook.md b/functions/what_is_my_ip/runbook.md
new file mode 100644
index 0000000..4b1963a
--- /dev/null
+++ b/functions/what_is_my_ip/runbook.md
@@ -0,0 +1,32 @@
+# Background
+
+The `write_file` function has wo parameters.
+
+* `path`: is a relative path from some project_root
+* `content`: is the content that should be written into the file
+
+## Usage
+
+This function should be given a rw bind mount for the root of a project.
+
+```sh
+docker run --rm --entrypoint /app/result/bin/entrypoint vonwig/what-is-my-ip:latest
+```
+
+## Build
+
+```sh
+docker build -t vonwig/what-is-my-ip:latest .
+```
+
+```sh
+# docker:command=build
+
+docker buildx build \
+    --builder hydrobuild \
+    --platform linux/amd64,linux/arm64 \
+    --tag vonwig/what-is-my-ip:latest \
+    --file Dockerfile \
+    --push .
+docker pull vonwig/what-is-my-ip:latest
+```